1. Field of Invention
The invention relates to image processing, particularly of detected sub-regions within face images.
2. Description of the Related Art
Proctor and Gamble's U.S. Pat. No. 6,571,003 mentions finding and fixing facial defects such as spots, wrinkles, pores, and texture in sub-regions of faces, e.g, cheeks or in areas defined by landmark points such as corner or nose, eye, or mouth. The technique involves replacing the defined region with a mask. The P&G patent discloses to electronically alter the color.
The P&G patent also mentions detecting and correcting lighting gradients and lighting variances. These lighting gradients, or variances, appear to involve instances where there is directional lighting which may cause a sheen or brighter region on the facial skin. U.S. patent application Ser. Nos. 12/038,147, 61/106,910 and 61/221,425, which are assigned to the same assignee as the present application and are hereby incorporated by reference, describe techniques which use Viola-Jones type classifier cascades to detect directional lighting. However, determining and correcting a lighting gradient would typically involve global analysis, exceptions being possible in combination with face-tracking techniques such as those described at U.S. Pat. Nos. 7,403,643 and 7,315,631 and U.S. application Ser. Nos. 11/766,674, published as 2008/0037840, and 12/063,089, 61/120,289, and 12/479,593, which are all assigned to the same assignee as the present application and are hereby incorporated by reference. It is desired to have a technique that uses a local blurring kernel rather than such techniques involving less efficient global analysis for certain applications and/or under certain conditions, environments or constraints
Kodak's U.S. Pat. No. 7,212,657 illustrates at FIGS. 13-14 to generate a shadow/peak image (based on generating a luminance image and an average luminance image), a blur image, and blended images. The Kodak patent states that a shadow/highlight strength image is generated by subtracting an average luminance image from a luminance image. Also, at FIG. 16, the Kodak patent shows element 1530 is labeled as “generate luminance and chrominance scaling factors using peak/valley map and color info”, and element 1540 is labeled as “modify luminance and chrominance of pixels within mask regions”. Face detection is described in the Kodak patent, but not face tracking.
The Kodak technique, like the P&G technique, involves global image manipulations, i.e., the “luminance image” is not indicated as including anything less than the entire image, the “blur image” involves the application of a kernel to the entire image, and the “blended image” involves three copies of the global image. The “blur image” involves chrominance and luminance data meaning that a lot of memory is used for manipulating the image, particularly if the application involves a resource constrained embedded system. Regarding luminance and chrominance scaling factors, even if they involve localized scaling factors, they are not described in the Kodak patent as being generated for application to anything less than the entire image.
U.S. patent application Ser. Nos. 11/856,721 and 12/330,719, which are assigned to the same assignee as the present application and are hereby incorporated by reference, describes a technique that can be applied as a single, raster-like, scan across relevant regions of an image without involving global analysis or a determination of global properties such as the average luminance image, or a shadow or blur image. Such single-pass scan through predetermined regions provides a far more efficient and suitable technique for embedded systems such as digital cameras than either of the P&G or Kodak patents.
The Hewlett Packard (HP) published patent application 2002/008.1003 mentions air-brushing which typically involves applying color over a swath of an image, e.g., such as may include a blemish or wrinkle. The HP publication also mentions blurring over a wrinkle on an image of a person's face, and again specifically describes blurring or blending color values defining the wrinkles and surrounding skin. The HP application mentions changing brightness to brighten or darken a facial feature, such as to shade a facial feature, and goes on to describe changing color values of skin associated with the feature to shade the feature. The HP patent further discloses to sharpen a hair line and/or blur a forehead and/or cheeks, by blurring color values. Face detection and face tracking over multiple images, full resolution or low resolution and/or subsample reference images such as previews, postviews and/or reference images captured with a separate imaging system before, during or after capturing of a main full-resolution image are not described in the HP patent, nor is there any suggestions to smooth or blur luminance data of a digital face image.
Portrait is one of the most popular scenes in digital photography. Image retouching on portrait images is a desirable component of an image processing system. Users can spend a lot of time with conventional software trying to make a portrait nicer by hiding wrinkles and blemishes. It is desired to provide an innovative automatic portrait scene enhancer, which is suitable for an embedded device, such as a digital still camera, camera-phone, or other handheld or otherwise portable consumer appliance having image acquisition components (e.g., lens, image sensor) and a processor.